Vulcanizing mold for tire casings



. J. R. GAMMETER.

VULCANIZING MOLD FOR TIRE CAS'INGS.

- APPLICATION FILED JULY 25,1921.

1,417,599. Patented May 30, 1922'.

my 1 o Job 1? fiammeter fizvezz for 01* NEW YOREI,'1-T. A CGRPQRATIGN or NEW 201m VULQAIKIZLNG MOLD F0; TIRE CASYN'GS,

ifipplicatla. filed July 2 '1 o mam/11, 122 is may coin/6M1:

lie known that I, Jo n: Gmmxnm, a viiizen of film lniled Strata's, residing a" Akron, iii the coimty of Summit and Stall? 5 of *lliiQ. have inveiiied a certain new and awful Vuluanizizig lliloid for Tire Casings, of which the following is a speoifioation,

1i veniun to the art oi Vulcan i pneumatic tires on their maodrels in 1Q mot l molds, and; its principal object is to f; lcle impi-o d means for causing the (:21 si o be. molded as (.l(+ill(l without substantiall displacing the fabric or (:2 rows elo- 5 meats, and WlllllOlIt mm'l'mg the rubber sm 15 has): by the presence of air or moisture liel3W- n the mold and the tire. Y

i l :mcompzmymg drawings:

5, Vernon} section of an openizeit press containing a staol; of

' Lire molds eon trusted according to my inw'mltiozil wluol Willa onto? side 'wall and trezul rubber, bimilrr sl'l'rip and llfillil elements, Stxwghti ls are here EllOWl'i, but they miglii be "j e, and n HOD-Slilifl trend is .1 invention also) applios smooflz-h'iziil casings. ll. mandrel. or more which 11 luring "vulc-"nliiqtion and, is;

*" i the tire i inextemsil ile- 1 one, 9 and bolts 1?.

bile Hit mold COIYKPOSEil of two 15., onclosing the Lire as Wfll as the poi'lion anal tlioss portions of the n lire... Zihile these mold memmade of @2155 from UK any other o Emmi I prefer to li s eel, machined toil l ape i .2, particulm'ly when the mold emthe spring Qlmz'aoteristic forming #1 Specification of Letter s Eatent.

lan View of one or" the molds.

make them (iii;

1921. Serial No. 87,446.

feature of my invention, since its use enables the mold to liemade light, strong, compact and with a minimum volume of metal to be :arried. through the heat cycle of the vullmnizing process.

Each mold memlie 15 is provided in its outer margin with a cii'ouinferential series of clefts or slain; 16, 16 made by thin S8,: or n'iilling tool in substantia ly radial planes transverse to llle plane the'mold and of :1 greater or less number limos-(ling to the size of the mold, there being here shown ten of these slots, (,llHPOSQQl at regular intervals registering in the two halves. These, slots uxfieml $0 the middle plane of Separation 1mm :11 the mold mggnbers, so that the .werl'low ins of rubber which exude into them from. film tire during the mohjling operation will connect with the oircimiferenlzial 02: middle fin or rand of overflow rubber, and they also prefomlily extend, as shown, to the outer edge of the mold and to its upper and lower surfaces. They cavity for enough on bol'h sides to take in the thickest pm of the Head or supporting; surface of the tire, and n'my laminate in this (liiQQ'L-ifin or less around on tho sides of ll-a Eire. The 1 ll of UHSE clofl's,

and zuljacont t the up um liolziom sub faces of the mold, is such as to illll il lil the desired degree of flexibility to the iimcrng iota: segn'lenl's of metal, and pl'P-ffll'fillly abom'; 1? same there as at the panting vplane. PS

j be less blum the minimum in bet-w as shown, clepeiuling aomewlizat upon I mm P9 of the ZI'IZHflllEllflg opoi'ation in making i1 secure-i by the usual :lowols (not Shown) and by the usual ll-f: 1. fornmiion w; 17, ml zuent to wlnvn shown the usual annularover-film :lmnne 18. if 19 are. prying {langos (H! the (flZ'ClHXlflEPHCGS of the molol members. The top 21ml bo 0m smrfzm-r-s 20, 20 oi the mold in fi ing normal or lncompro. wil condition o? is mombez's aro siligi litlv inolinal" oauavoly coiml, as mp1 4 the inomberr-z' an'nnlzi ix malis il utively Irihin p'ori'zlolsm 22- lm'viog sufficieni flexibility to alloral longing: miioii of film mold walls over the widen:

: po'z'tlons of the core body, adjacent to the beads of the tire casing Thg mold members are also Ezllmilml May 36, 1%.?22.

extend transversely of the mold slightly open at the tread or outer periphery until sufficient axial pressure is exerted to close them at the tread. It is possible. however, to obtain some of the important, ad-

' vaiitages of my invention by using the radial clefts 16 merely as an improvement in a mold of ordinary construction whose top andv bottom surfaces are always parallel or made permanently of the form shown in Fig. 4.

In the preferred mode of operating my invention, a core 11, with a tire casing built up thereon, is placed in the mold 14 and a stack of Such molds located between the top and bottom plates 24, 25 of a vulcanizer press such as the press 26 shown in Fig. 1, this view, showing an opensteam pot press vulcanizer of familiar type. The molds are then put under sufficient hydraulic pressure substantially to close them together at the beads and to keep these portions of the tire firmly confined between the core and the mold from the beginning of the heating period. The best results are obtained if the mold members 15 are fairly hot when the tire is placed between them, so that the raw rubber in the tire quickly tends to become soft and plastic. This condition may be obtained, for example, by emptying and tilling the molds in a comparatively brief time. so that they retain a considerable part of their heat from the previous vulcanizing operation. The hydraulic pressure in the 'initial stage will be such that the mold members 15 do not come together at the tread or outer periphery but will sufficiently compress and indent the rubber-at the margins or shoulders of the tread zone to seal oil the mold cavity at the sides of the tire against the entrance of the steam which it is preferred to use as a heating medium. Steam being admitted to the interior of the vulcanizer to surround and heat the molds 14: and the tire cords 11, the rubber then be- -comes' very plastic and readily flows to fill the non-skid tread markings and other recesses in the mold and to permeate the fabric and bead elements of the tire. between the cross-sectional dimensions of the raw tire and the mold cavity is preferably such that while the tire casing 10 is tightly clamped between the mold and the core at the beads, there is a slight clearance or at least only a Very light pressure between the mold and the sides of the tire from the The relation region adjacent to the beads outwardly to the tread.

After the lapse of a suflicient period for the tire to become thoroughly hot and soft, the mold may be completely closed thereon. as shown in Fig. 4, by the application of sufficient hydraulic pressure to spring the members 15 together at the tread, and the vulcanization may then proceed to comple-'" tion with the mold thus closed. The initial heating period'with the mold in the condi-- tion shown in Fig. 3 may be such as merely to soften the rubber without causing it to become set or vulcanized by the action of the sulfur and accelerator with which it is compounded, or the heating. under these conditions may be carried far enough partially to set or cure the rubber on the plies of the carcass, and thus aid in holding the threads of the carcass against relative displacement by the flow of the rubber toward the tread of the tire. In either case the molding of the tire substantially to its ultimate configuration is or may be substantially complete at the end of the initial stage of heating. before complete closure of the mold, and this molding takes place under a considerable degree of pressure by reason of the swelling of the rubber, usually with the formation of substantial overflow tins or rands (not shown in the drawings) in the various radial clefts l6 and in the circumferential cleft at the parting plane, so that the rubber at the end of the initial stage is found to be dense in texture and free from blisters or sponginess. By way of example, if the total heating period for a complete cureis fifty minutes, the initial heating stage with the mold sprung open at the tread may be of ten minutes duration without a substantial amount of settin or curing, or it may be oftwenty minutes duration with a partialsettiug of the rubber in the carcass, this rubber being properly compounded with relation to the tread and side-wall rubber to give the desired effect. The final cure in the fully-closed mold may then be for a period of forty or thirty minutes. causing a complete setting of the rubber in both the carcass and the tread and side-wall portions under such-I conditions as to increase its densification and produce the desired degree of compactness in all parts of the tire. The initial heating and flow of the rubber at the surface of the tread and side walls having occurredunder conditions of relatively light pressure, it is found that the fabric in thecarcass remains substantially in the position in which it was laid, so that theplies are smooth and free from buckles or creases. I

My invention considered as a spring mold has the advantage over prior molds of the same general type that the fabric in the carcass may be firmly anchored and molded I80 at the beads While the initial flow of rubher is taking place, before the mold is closed at the tread. i

The transverse radial-clefts 16 also have the important function of acting as vents for the discharge of any air or water of condensation which might tend to become pocketed between the mold and thesides of the tire and thus mar the surface formation, and I may employ this improvement in an ordinary mold not having the spring feature as previously indicated, with the result that a perfectly-formed tire of increased durability, by reason of having a less highly compacted structure, may be produced by employing pressure than. has heretofore been necessary.

Various other changes in construction and mode of procedure may also be effected Without departing from the scope of my invention, for example, by using a spring mold or one having an initial clearance from the tire at the sides and between the. mold memhers at the tread, While "fully closed upon the tire at the beads, substantially as repre sented in Fig. 3, and allowing it to remain in such relation to the core 11 throughout the entire vulcanizing period. Or, the hill hydraulic pressure for progressively closing, the mold of Fig. 8 toward and at its outer periphery may be applied as soon as the molds are placed in the vulcanizer and the latter eiosed, the steam being then turned on and the tire heated and vulcanized in. the fully-closed mold.

I claim:

' corn r-rising pair of conmembers formed with a moiding cavity, said mold having its tread portion transected by a.- series of venting slots.

'lire-molding apparatus comprising a rigid core, and an enclosing mold composed of men'ih-ers formed in their tread-molding portions with a oircumferentially-disposed series of transverse venting slots extcndin from the outer edge of the mold radially inward and terminating at points corresponding substantially to the side margins of the groundcontacting portion of the tire.

3. Tire-molding apparatus comprising a, rigid core, and a pair of annular spring a smaller degree of hydraulic cry.

molding members normally. tending to separate at the tread while in closed relation with the core attheir inner periphery.

4:. Tire-molding apparatus comprising a core, and a mold formed with transverse tread slots and including a pair of annular molding members normally tending to spring open at the tread While closed at the beads.

55. A tire mold comprising a pair of annular spring members formed with a molding cavity and transverse slots connecting said cavity with the outer edge of the mold, said mold having normally concave top and bottom pressure-transmitting surfaces.

6. A tire mold member comprising a rin formed Withsubsta-ntially one-half ofa tiremolding cavity on its inner surface, a continuous bead and side forming portion, a tread-forming portion transected by radial slots dividing it into spring segments integral With said bead and side forming portion, and annular concentric pressure-trans mitting surfaces on the outside of said member, separated by a groove forming a relatively-thin. hinging Wall over the side-molding portion of the tire cavity adjacent the bead-moldingportion, the surface of larger diameter being normally farther from the median plane of the molding cavity than the one of smaller diameter and adapted to be brought to the same level therewith by pressure used in closing the mold at its outer periphery 7. Tire-molding apparatus comprising a rigid core having body and tongue portions, a pair of anuular mold members enclosing; said core and transected by radial slots dividing their outer margins into spring segments, said membersnormall springing apart at the tread While closed against the core tongue at the beads and having concentric, annular, pressure-transmitting surfaces separated b annular grooves, the surfaces of larger diameter being normally "furtlier apart but adapted to be brought level with "those of smaller diameter by pressure used in closingthe mold at its outer periph- JOHN R. GAMMET'ER. 

